How to find the index of a randomly chosen element of an array

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feit feit
feit feit 2020-12-2
评论： Ameer Hamza 2020-12-3
Would anyone suggest me the code of finding out the index of a randomly selected element of an array or matrix?
For example, after randomly selecting an element from 'a', I want to find out the index number of the chosen element. This index number should be a variable as each time i randomly select an element, the corresponding index number of the selected element may change.
a = [4 5 10 15 20];

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Ameer Hamza
Ameer Hamza 2020-12-2
Try this
idx = find(a==random_element)
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feit feit
feit feit 2020-12-3
Row number is the criteria. I will have a row number (which is also a variable) and i only need the combination corresponding to that particular row number.
Ameer Hamza
Ameer Hamza 2020-12-3
You can just apply find() to that row
a = [ 1 3 4; 1 4 5; 2 1 6];
row_num = 3;
random_element = 1;
col_num = find(a(row_num,:)==random_element)

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Steven Lord
Steven Lord 2020-12-2
Ran in:
Start off generating the index and use it to extract the element.
a = [4 8 15 16 23 42];
I = randi(numel(a));
fprintf("Element %d of a is %d\n", I, a(I))
Element 5 of a is 23

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